1. Field of the Invention
This invention relates to a component interface module that arbitrates component command signals received from redundant systems, and integrates them with component feedback signals to generate component control signals. The component interface module incorporates diagnostic functions that take into account component state as reported by the component feedback signals.
2. Background Information
Certain complex plants integrate control signals from redundant systems to generate actuation signals for plant components. An example is a nuclear power plant, which utilizes a control system and a safety and protection system that independently utilize diverse sensors and logic to generate control signals for pumps, motors, contactors, solenoids, switchgear, and the like. In addition, manual control signals are integrated with the automatic signals. It is necessary to arbitrate the command signals from these multiple sources to generate the control signal for the component. Typically, the manual signals are given the highest priority. Signals generated by the automatic systems can be assigned priority in two ways: either one system has absolute priority over the other, or a command in one direction (e.g., open or closed, off or on) from either system has priority over a command in the opposite direction. A recently developed system implements priority between the automatic signals and the manual signals in a component interface module having output relays generating control signals sent to the component.
For reliability, the priority logic is non-software based and is commonly implemented in hardware such as gate arrays with the options on priority selected by jumpers.
The various components can have their own requirements for the actuation signals. For instance, contactors require a continuous control signal while motor operated valves only require a control signal during movement of the valve member. In the latter case, the control signal needs to be terminated to prevent burnout of the relay generating the control signals. Typically, such components have position limit switches and often also have torque limit switches. A position limit switch can be used to indicate that the valve has opened. Another can be used to indicate a closed valve, although in some circumstances where full closure of the valve is essential, the torque limit switch provides the closed indication.
At present, the component logic, that is the logic associated with, for instance, the component position and torque limit switches, is implemented at the component, and at the actuating power level of the component, even in the above-described system that combines the automatic signals and the manual signals in a component interface module.
There is room, therefore, for improvement in the interfaces between plural systems generating component command signals and the components they control.